A large number of veterans returning from the Persian Gulf region have reported health problems. Among the most frequent complaints are fatigue, muscle pain, and muscle weakness. In an effort to characterize the muscular aspects of this illness we are studying skeletal muscle energetics in the veterans with chronic fatigue and muscular weakness. To date, 9 PG veterans were studied using MRI, MRS, and Isometric and Isokinetic testing. In addition, 6 out of 9 veterans underwent a comprehensive physical and history prior to testing in the search for any diagnosable illnesses that could cause the same symptom complex. The 31P-MRS data indicated that the mitochondrial function of skeletal muscle may be impaired. The rate of PCr resynthesis, a measure of the in vivo oxidative capacity, was two-fold slower in the veterans than in healthy sedentary subjects (n=15). The degree of mitochondrial impairment assessed via MRS correlated with the health status of the veterans. The veterans who were the most severely affected, demonstrated the lowest oxidative capacities. In contrast, individuals who were relatively functional had the highest oxidative capacity. Measurements were performed on the right calf during isometric and isokinetic contractions at different angular velocities to quantified the muscular strength and endurance in the veterans.. At all angular velocities the mean peak torque of the veterans was lower than that of healthy control subjects. In conclusion our preliminary data indicate that muscular abnormalities may contribute to the symptom profile of veterans. Even more importantly, the rate in vivo oxidative capacity correlated well with the health status of the veterans.